1. Field of the Invention
This invention relates to a coordinate measuring machine, and more particularly to a coordinate measuring machine wherein a probe is moved in three axial directions including X, Y and Z-axis to measure a shape of a workpiece.
2. Description of the Related Art
A 3-dimension coordinate measuring machine is adapted to move a probe in three directions including X, Y and Z-axis to thereby measure a shape and the like of a workpiece. As shown in FIG. 3, a moving mechanism in the direction of the Z-axis (vertical direction) of the 3-dimension coordinate measuring machine has a Z column 10 which is implanted in an X carriage 11 supported movably in an X direction along an X-axis guide 12. A pair of rollers 14 and 16 are rotatably supported at the top end portion of the column 10. A wire 18 is guided around the rollers 14 and 16, and a Z carriage 20 and a balance weight 22 are connected to one end portion and the other end portion of the wire 18, respectively.
The weight of the balance weight 22 is equal to the weight of the Z carriage 20.
Furthermore, a DC servo motor, not shown, is connected to either one of the rollers 14 and 16, and, when the DC servo motor is driven, the Z carriage 20 moves up and down by the wire 18. Accordingly, a probe 24 provided on the Z carriage 20 is positioned at a predetermined position.
However, in the conventional Z-axis moving mechanism, there is a need for raising the bottom end portion of the Z carriage 20 to the X guide 12 during the measuring, whereby it is necessary to set the height of the Z column 10 to a value at least higher than the Z carriage 20. Accordingly, the more the weight of the X carriage is increased, the higher the position of center of gravity becomes, whereby it becomes disadvantageous for moving the X carriage and a Y carriage smoothly, thus causing a hindrance in the accuracy improvement. Furthermore, as a result, the height of the coordinate measuring machine is increased, whereby such disadvantages are caused that, when the ceiling of a building is low, it is difficult to install the coordinate measuring machine, and further, the column 10 should be inclined or removed during the transportation.